1. Field of the Invention
This invention relates to an improved fuel injection valve and to a method of producing the valve.
2. Description of the Prior Art
From the prior art, various methods for hardening steel are known. The intent is to vary the wear resistance and durability of the material as well as its workability. One example is known as case-hardening or carburization, in which carbon is incorporated into the layers near the surface of the workpiece. One method in this respect is described in U.S. Pat. No. 4,836,864, for instance. Other possibilities are nitriding of steels, in which nitrogen is incorporated into the layers near the surface of the workpiece. In fuel injection valves as well, of the kind used preferably for self-igniting internal combustion engines and described for instance in German Patent Disclosure DE 196 18 650 A1, the use of such hardened and treated steels for lengthening the service life of the steels is also known. In the course of further development in engines, the temperature stress on the fuel injection valve and thus on the needle seat in the valve body will continue to increase because of an increase in performance or an enhancement in the braking power, especially in utility vehicles. The carburized steels used until now, and the hardening methods employed for them, are no longer sufficient for these applications.